The present invention relates to a method for increasing the lift of an aerodynamic surface of an aircraft and for reducing the drag of an aerodynamic surface on a ground vehicle. The invention has been devised for application, in particular, to the wings of aircraft, as the following description will make clear, but the invention can also be used to improve the aerodynamic efficiency of an aircraft in general or that of a ground vehicle.
When taking off and landing, modern aircraft require a capacity for increased lift, in other words the possibility of enhancing the normal capacity of the wings to keep the aircraft flying at the reduced speed at which they operate in these conditions. This effect is typically obtained by the downward deflection of the flaps.
In the past, it has been proposed that air at high pressure should be drawn from the jet engine and blown at supersonic velocity on to the upper surfaces of the flaps through a passage running along the rear edge of the fixed part of the wing, in order to increase the efficiency of the increased lift devices in fighter aircraft. The energy supply created by this jet of air retards the loss of vacuum which occurs on the upper surfaces of the flaps when the reduced flight velocity makes the air stream flowing over the wing tend to break away from the wing, causing a loss of lift.
The use of this method, as applied in the past, is not possible in more modern aircraft, particularly civil aircraft, whose jet engines cannot supply the requisite quantity of pressurized air. This limitation is inherent in the method, since it requires the use of a blowing velocity well above the speed of sound, which would require very large amounts of air, especially because the wing area of modern aircraft, whether military or civil, is very large. In any case, the air flow provided in this way would be insufficient for large aircraft.
As an alternative, the compressed air could be supplied by a suitable compressor, but this would entail an unacceptable increase in cost, weight and energy consumption.